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Allergy Treatment


Antihistamines and decongestants are the two main allergy medication types.


Antihistamines block the action of histamine, the substance released when mast cells recognize the presence of allergens. Antihistamines relieve redness, inflammation, itchiness and watery eyes. Ophthalmic solutions (drops) for the eye can also relieve red, irritated eyes. Many older antihistamines have a sedating effect. They make you sleepy. Newer, non-sedating ones are available, most by prescription. A dry mouth is also a common side effect. It helps to have liquid antihistamines as well as those in pill/capsule form, as they are more easily swallowed during a stronger allergic reaction.


Decongestants reduce nasal congestion by constricting blood vessels. Nasal sprays work faster than oral decongestants, but "rebound" is also common. After a few days of taking nasal decongestants, there's a "rebound effect" in which the congestion that had cleared comes back. More medication only makes the congestion worse. Discuss this side effect with your doctor to understand how to limit the amount of medication you use.


Bronchodilators relax the muscles around the air tubes in the lungs. They decrease allergy symptoms such as coughing, wheezing and shortness of breath. Agitation and nervousness are common side effects.

Steroid Medications

Steroid medications in oral or inhaled nasal forms are used to decrease inflammation. Nasal steroids have fewer side effects than oral forms. Long-term oral use (more than one week) must be carefully monitored by a doctor, because of potential systemic side effects. Low-dose topical steroid medications are used for rashes.

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Immunotherapy (Allergy Shots)

Some people with allergic asthma can't easily control symptoms by avoiding triggers and using medication. For them, immunotherapy (allergy shots) may offer relief and even help prevent development of airway inflammation and the resulting chronic airway sensitivity.

How do allergy shots work?

Allergen immunology works like a vaccination. Through exposure to small, injected amounts of a specific allergen in gradually increasing doses, your body builds up immunity to the allergen(s) that trigger an allergic reaction. This means that when you encounter these allergens in the future, you will have a reduced or very minor allergic response and fewer symptoms.

Who should get allergy shots?

Immunotherapy works best for those with allergies to pollen, mold, cat dander, insect stings and dust mites.

Are there side effects?

Potential side effects during treatment may include swelling at the site of the injection and in rare instances a more serious allergic reaction, causing asthma symptoms or an anaphylactic reaction. Asthma symptoms include cough, wheezing and shortness of breath. Symptoms of an anaphylactic reaction can include hives, sneezing, watery nasal discharge, itchy eyes, swelling in the throat, wheezing or a sensation of tightness in the chest, nausea, dizziness or other symptoms.

What do allergy shots involve?

Immunotherapy involves injecting small doses of the allergic substance to help produce more antibodies, which strengthens the resistance against the allergen. This approach has been helpful for pollens, molds, mites, insects and animal dander. The doctor makes a schedule of weekly shots, gradually increasing the strength of the allergen injected, based on the previous week's response. Patients are asked to wait about 20 to 30 minutes after the injection to make sure there are no adverse effects. The site is inspected after the waiting period, with any redness, bumps or swelling noted. The area affected is measured and the next dose is based on those results.

People with multiple allergies can get several shots, following the same procedure. Very fine needles are used for the injections, and the needle only goes just below the skin's surface. While the needle rarely causes discomfort, the solution being injected can be irritating and cause itchiness or a stronger reaction. An allergist may prescribe immunotherapy for children to be given in the pediatrician's office. In that case, the office personnel should have CPR training and be equipped to handle rare, severe reactions.

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Contact Information

Allergy and Inflammation - Research
Department of Medicine
Beth Israel Deaconess Medical Center
Center for Life Science, 9th floor
330 Brookline Avenue
Boston, MA 02215